Thanks for the reply Oliver, much appreciated.
olikraus:
Option 1 (high speed solution):
You change procedure u8x8_byte_ks0108 (and u8x8_byte_set_ks0108_cs) in this file:
u8g2/csrc/u8x8_byte.c at master · olikraus/u8g2 · GitHub
Basically, any calls to
u8x8_gpio_call()
has to be replaced by a custom function, which would set the pin through your 595.
Just those two functions? Great!
So...
void u8x8_byte_set_ks0108_cs(u8x8_t *u8x8, uint8_t arg)
{
u8x8_gpio_SetCS(u8x8, arg&1);
arg = arg >> 1;
u8x8_gpio_call(u8x8, U8X8_MSG_GPIO_CS1, arg&1);
arg = arg >> 2;
u8x8_gpio_call(u8x8, U8X8_MSG_GPIO_CS2, arg&2);
}
This code just sets the CS1 & CS2 pins. But reading the code, I can't figure out which bits in arg do what.
Bit 0 of arg seems to be some kind of overall Chip Select pin. Is that irrelevant for KS0108, because it has CS1 & CS2?
Bit 1 of arg sets CS1. Easy.
But it looks like Bit 4 of arg sets CS2? arg gets shifted right by 3 bits, then bit 1 is masked.
Does Bit 3 of arg do anything?
uint8_t u8x8_byte_ks0108(u8x8_t *u8x8, uint8_t msg, uint8_t arg_int, void *arg_ptr)
{
uint8_t i, b;
uint8_t *data;
switch(msg)
{
case U8X8_MSG_BYTE_SEND:
data = (uint8_t *)arg_ptr;
while( arg_int > 0 )
{
b = *data;
data++;
arg_int--;
for( i = U8X8_MSG_GPIO_D0; i <= U8X8_MSG_GPIO_D7; i++ )
{
u8x8_gpio_call(u8x8, i, b&1);
b >>= 1;
}
u8x8_gpio_Delay(u8x8, U8X8_MSG_DELAY_NANO, u8x8->display_info->data_setup_time_ns);
u8x8_gpio_call(u8x8, U8X8_MSG_GPIO_E, 1);
u8x8_gpio_Delay(u8x8, U8X8_MSG_DELAY_NANO, u8x8->display_info->write_pulse_width_ns);
u8x8_gpio_call(u8x8, U8X8_MSG_GPIO_E, 0);
}
break;
case U8X8_MSG_BYTE_INIT:
/* disable chipselect */
u8x8_gpio_SetCS(u8x8, u8x8->display_info->chip_disable_level);
/* ensure that the enable signal is low */
u8x8_gpio_call(u8x8, U8X8_MSG_GPIO_E, 0);
break;
case U8X8_MSG_BYTE_SET_DC:
u8x8_gpio_SetDC(u8x8, arg_int);
break;
case U8X8_MSG_BYTE_START_TRANSFER:
/* expects 3 bits in arg_int for the chip select lines */
u8x8_byte_set_ks0108_cs(u8x8, arg_int);
u8x8->gpio_and_delay_cb(u8x8, U8X8_MSG_DELAY_NANO, u8x8->display_info->post_chip_enable_wait_ns, NULL);
break;
case U8X8_MSG_BYTE_END_TRANSFER:
u8x8->gpio_and_delay_cb(u8x8, U8X8_MSG_DELAY_NANO, u8x8->display_info->pre_chip_disable_wait_ns, NULL);
u8x8_byte_set_ks0108_cs(u8x8, arg_int);
break;
default:
return 0;
}
return 1;
}
I have to modify the above to send bytes to the display via the registers. I think I understand what I need to do for message U8X8_MSG_BYTE_SEND, which is the most complex. For U8X8_MSG_BYTE_INIT and U8X8_MSG_BYTE_SET_DC, there is not much to be done. For U8X8_MSG_BYTE_START_TRANSFER and U8X8_MSG_BYTE_END_TRANSFER, I can't figure out what, if anything, I need to do. Can I leave those as-is?
Here is my test code which produced the pattern shown in the picture above, in case it is important. It's very short.
#include <SPI.h>
// D5 and D7 used as SPI bus to drive 2 x 74hc595 Shift Registers
SPISettings sn74hc595(100000000UL, MSBFIRST, SPI_MODE0);
#define LATCH D8
//Shift register pins controlling KS0108 Graphic LCD
// GLCD_RS: H = data, L = instruction
#define GLCD_E D0
#define GLCD_RS 6
#define GLCD_CS1 5
#define GLCD_CS2 7
byte control = 0;
void sendGLCD(byte data) { //Send a byte to the GLCD
digitalWrite(GLCD_E, HIGH);
digitalWrite(LATCH, LOW);
SPI.transfer(control);
SPI.transfer(data);
digitalWrite(LATCH, HIGH);
digitalWrite(GLCD_E, LOW);
delayMicroseconds(5);
}
void setup() {
SPI.begin();
pinMode(LATCH, OUTPUT);
pinMode(GLCD_E, OUTPUT);
bitSet(control, GLCD_CS1);
bitSet(control, GLCD_CS2);
bitClear(control, GLCD_RS);
SPI.beginTransaction(sn74hc595);
sendGLCD(0b00111111); // Enable display
sendGLCD(0b11000000); // Set Scroll Position = 0
SPI.endTransaction();
}
byte i = 0;
void loop() {
SPI.beginTransaction(sn74hc595);
for (int x = 0; x < 8; x++) {
bitSet(control, GLCD_CS1);
bitSet(control, GLCD_CS2);
bitClear(control, GLCD_RS);
sendGLCD(0b10111000 | x); // set X
sendGLCD(0b01000000); // Set Y = 0
bitSet(control, GLCD_RS);
bitSet(control, GLCD_CS1);
bitClear(control, GLCD_CS2);
for (int y = 0; y < 128; y++) {
if (y == 64) {
bitClear(control, GLCD_CS1);
bitSet(control, GLCD_CS2);
}
sendGLCD(i++);
}
}
SPI.endTransaction();
delay(500);
i++;
}
